High Performance and Durable Membrane Electrode Assemblies with Binder-Free Plasma Sprayed Electrodes and Nanocomposite Membranes for Anion Exchange Membrane Electrolyzer
Hydrogen production via water electrolysis using electricity from renewable power sources is a promising method for storing energy in a large scale. Anion exchange membrane (AEM) electrolyzers have the potential for decreasing the hydrogen cost produced by renewables due to use of non-noble materials and inexpensive components for the membrane electrode assembly (MEA). This work demonstrates a highly active and durable MEA for AEM electrolysis using binder-free atmospheric plasma sprayed (APS) RANEY-type nickel and RANEY-type nickel-molybdenum electrodes, as anode and cathode, respectively in combination with robust two-dimensional hexagonal boron nitride (h-BN)-based anion exchange membranes, nanocomposed with either polyvinylidene fluoride (PVDF) or polyvinyl alcohol (PVA). In this present work, various AEMs with different ionic conductivity and thickness, M1: High-loaded h-BN nanocomposite with PVDF or HL-BN-PVDF (0.23 Scm~(-1) and 125 mμ), M2: low-loaded h-BN nanocomposite with PVDF or LL-BN-PVDF (0.19 Scm~(-1) and 80 mμ) and M3: high-loaded h-BN nanocomposite with PVA or HL-BN-PVA (0.36 Scm~(-1) and 45 mμ) have been used. Three MEAs were fabricated using three membranes of HL-BN-PVDF, LL-BN-PVDF and HL-BN-PVA placed between two APS electrodes denoted as The MEA1, MEA2 and MEA3, respectively, and tested in single AEM electrolyzer cells. The tests are carried out in 1M KOH at 60°C. As expected, the highest current, 2.6 Acm~(-2), at 2 V is achieved with MEA3, while MEA2 and MEA1 reached 2.95 and 3 A cm~(-2), respectively. The performance of AEM water electrolysis with the MEA3 is found to be slightly better than the MEA with the same electrode package but commercial membrane from Fumasep (2.71 Acm~(-2) at 2.0 V). The stability of the cell with MEA3 is tested under the constant load of 0.5 A cm"~2 for 250 h showing negligible degradation. This can be attributed to the high mechanical and chemical stability of the membrane and low dissolution of anodic electrode. Furthermore, the lack of binders or ionomers in the APS electrodes avoids irreversible oxidation reactions of the polymer that can lead to voltage loss over time. Thus, APS electrodes combined with stable nanocomposed (h-BN)-based membranes can potentially lower the cost of the hydrogen produced by water electrolysis.
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